I live at La Crescent, MN but my comment about someone helping was made tongue in cheek. I got up early this morning and got the coolant drained and some of the lines off before my medical appointments. I will get back at the job after lunch. It looks like the worst part will be getting to some of the mounting bolts and putting them back will be even harder. I enjoy challenges, so this is just another one. My neighbor is good about giving me a hand when needed so that helps too. I will take your advise about getting a new unloader kit. I just hope I don't need a rebuilt compressor.

I got the compressor off and found the problem. It is a drive problem, but not a sheared key. The drive coupling on the compressor is made of a bakelite like material around a steel center, with a key slot, that goes on the crankshaft. The coupling is slipping where the bakelite part was attached to the steel center. It took me about 3 hours to remove the compressor from the engine after I had the coolant drained. One bolt and one coolant line were a bitch to get out. Otherwise not too bad. I will make a couple of modifications to make it easier to put those items back together. I will use two short studs to help align the compressor with the gear housing once it is in place. I called Curt at Central Truck and he has the coupling. Hopefully I can get everything back together so we can take the bus to a Midwest Bus Nuts rally on Friday.

The bakelite is intact except where it contacts the steel hub's splines. It seems to be worn smooth as if the internal splines of the bakelite sheared off from the center hub. There is only a small amount of residue inside the bakelite coupler. The engine ran only a short time after the compressor quit pumping air. Its almost time for an oil change anyway so I think I will change it after I get the compressor back on. Or at least have the oil analyzed.

I think I read once that those drive gears come with different number of teeth so you may want to research that or make sure the one you get is correct. I might be wrong but thought it was worth a mention.

Yours must be a 71 series Craig most of those had the fiber gear drive the 92's have a steel drive gear with the coated spline coupling you guys from Mn must be tough on compressor drives John Z lost one in Texas a few years back

Yours must be a 71 series Craig most of those had the fiber gear drive the 92's have a steel drive gear with the coated spline coupling you guys from Mn must be tough on compressor drives John Z lost one in Texas a few years back

I think we are talking about 2 different things here Craig I call the the drive gear the one that bolts to camshaft 4 bolts sorta of square the coupling goes into never saw a fiber drive on 92 series but anything is possible on these buses

The old Detroit's in a GM that drive was fiber so if it broke and fell on the gears no harm was done power steering pumps (Vickers) still use fiber flex coupling you find those in oil pans all the time with ground fibers nothing to be alarmed about it's by design

When I was cleaning parts and bolts, I noticed that the mounting bolt threads have some type of sealant on them. Any suggestions as to what type sealant to use when I reinstall the bolts? I will be putting the compressor back in tomorrow.

I think we are talking about 2 different things here Craig I call the the drive gear the one that bolts to camshaft 4 bolts sorta of square the coupling goes into never saw a fiber drive on 92 series but anything is possible on these buses

The old Detroit's in a GM that drive was fiber so if it broke and fell on the gears no harm was done power steering pumps (Vickers) still use fiber flex coupling you find those in oil pans all the time with ground fibers nothing to be alarmed about it's by design

Ok. I was referring to the gear on the compressor side. That's what broke on mine when the compressor seized.

I already had the compressor installed before I read your message. I used a Permatex product as a thread sealer since I didn't know if what was on the threads was a sealer or to prevent the bolts from loosening. The product I used should do both, as would loctite. The label is worn off the tube so I'm not sure exactly what it is, but it is red. I was able to get all but 1 gallon of coolant back into the system, so I must have an air bubble in there somewhere. I bled some air out the petcock on top of the thermostat housing. I will warm the engine up and see if the coolant level drops so I can get the last gallon in. Otherwise putting the compressor back in went well, but took about 5 hours. Good thing I could do the job myself, otherwise it would have gotten expensive. I hope I never have to do that job again.